Revealing mistake: When Jack is aboard the Black Pearl, as Will makes demands we see Jack's very grimy hands and dirt embedded fingernails. Jack dives and retrieves his sword and gun underwater, and when he does the hands that lift the sword and gun underwater are perfectly clean and have very well manicured fingernails. Once on the island, his hands are as grimy as they were on the Pearl and his fingernails are once again short and dirty. (01:34:50)
Continuity mistake: In Port Royal, during the pirates looting, the sign comes crashing down onto Grapple, and Will says, "Good bye." In the next wide shot, behind Will to his left are a large and small barrel up against the wall, the large one being right in the corner. As a passing pirate hits Will on the head with a candlestick, in this shot both barrels are now further from the corner and closer to the door. (00:35:15)
Continuity mistake: Near the end of the first scene of the Isla de Muerta duel, we cut from Will's fight to Jack and Barbossa (just before "You're off the edge of the map"), and we have a good view of the cave. Where did Will and the other pirates go? (01:52:40)
Deliberate mistake: The East India Trading Company in reality, branded pirates with a 'P' on their foreheads, never on their arms, the way Captain Jack has it. It was deliberately decided to be historically inaccurate, feeling it looked better on Depp's arm. (Confirmed on commentary.) (00:17:20)
Continuity mistake: When Captain Jack Sparrow steps from the sinking ship to Port Royal's dock, he lifts his right leg for the step-off. Yet, when the shot cuts to his feet hitting the dock, Captain Jack steps off on his left foot. (00:10:05)
Revealing mistake: In the wide shot, when an unconscious Elizabeth reaches the water's bottom, the body is a mannequin that has been weighted down in the middle. The white mannequin head can be seen as the body meets the bottom. (00:15:55)
Continuity mistake: Elizabeth, alone in her room, puts on her robe while standing near her bed, when her father knocks. He walks in with one maid who goes to open the curtains and doors and a second who's carrying the dress box. Yet, as her father inquires, "Still abed at this hour?" a third maid steps out from behind Elizabeth and goes to open the curtains and disappears again. This maid didn't come in with Governor Swann, nor any other doorway including the one behind Elizabeth. Obviously this was part of a longer shot, but she still appears out of nowhere. (00:05:45)
Continuity mistake: Jack and Will jump down from the beams and Jack reaches for the bag of soot (really cocoa powder). In the back shot of Will as he approaches Jack, Will has his sword in his right hand. In the front close-up of Will as Jack starts to spray him, his right hand is NOT holding the sword - we SEE his hand when he turns. In the next wide shot, Jack is still spraying the soot, Will is again holding the sword in his right hand, then Jack kicks the sword out of Will's hand. (00:26:15)
Visible crew/equipment: Elizabeth comes up from below deck and asks, "What's happening?" and Anamaria answers, "The Black Pearl, she's gaining on us." Anamaria is alone at the wheel at the stern of the boat. Elizabeth then steps up and leans over to get a better look at the Pearl. In the next shot, the side of Interceptor can be seen, and in the distance is the Pearl. In this shot, on deck behind the rigging we see a crew member's leg and some other hand movement, it is not Anamaria's nor Gibbs' leg. (01:21:30)
Visible crew/equipment: In the extreme close up of young Elizabeth's face, when she first sees the Black Pearl, the only things in front of her are 1) sky; 2) sea; 3) Black Pearl. Yet, in her eyes are reflected two big, round objects - filming spots or reflectors. (00:04:45)
Visible crew/equipment: When Will and the hangman go at it, there is a close-up of Jack. In that shot, when Jack turns to his left it's very apparent that under his shirt at his shoulders and back, there's an apparatus holding the actor up, in order to help him swing back and forth, and so the false noose wouldn't harm him in any way. (02:06:40)
Continuity mistake: Just before Elizabeth whacks Jacoby, she asks, "You like pain?" and in the first shot as she starts to swing her hair has some waves and curl to it. Mid swing it cuts to the second shot, and when she says, "Try wearing a corset!" her hair is totally flat with no waves or curls whatsoever. Then, in the very next shot it's actually full, wavy and curly. (01:59:45)
Visible crew/equipment: After Jack rescues Elizabeth, Norrington shows up on the dock and points his sword directly at Jack. In the first shot facing Norrington, (as the sword points toward the camera, which is Jack's POV), the clear reflections of crew members are visible on the large underside of the crossguard, at the hilt of Norrington's sword, when in fact the only one who should be in the reflection is Jack, or possibly even Murtogg or Mullroy. (00:16:50)
Revealing mistake: Koehler and Twig are with Jack in the prison when Koehler reaches for Jack's neck through the cell bars. In the first shot, the ray of moonlight is outside of the cell bars, over Jack's head, so Koehler's arm becomes skeletal while still outside the bars and we see the 'cursed' sleeve till the elbow. However, in the next shot, the ray of moonlight is only inside the cell where Koehler reaches, so Koehler's arm and sleeve are normal until it becomes skeletal, just when it's inside the cell. (00:37:00)
Visible crew/equipment: When the Black Pearl fires on Port Royal, during the cannon fire in the town, one of the stuntmen shouts as he is being propelled into the air by a spring board and then lands on a vegetable cart. The spring board is perfectly visible behind a wheelbarrow and sack. This occurs just before the first shot of the chimney exploding. (This is another stuntman and spring board than the other mistake.) (00:30:20)
Visible crew/equipment: During many close-ups of Jack, Will and other characters, either two side by side reflectors or a single large reflector screen are clearly reflected in their eyes. (00:16:45)
Continuity mistake: In the close-up of young Elizabeth, as she sings on the bow of the ship, she's standing between two posts of the railing. Each post has rope wound around it. In the next few shots of her, the existence, the amount and the thickness of the rope on each post changes drastically. (00:00:45)
Continuity mistake: In the cave, Ragetti is holding a parasol over his shoulder, rubbing his eye. In the close-up, as Pintel says, "Stop rubbing it," there's no sign of Ragetti's parasol, nor any shadow on his hair or shoulders, and the folded parasol that Pintel is holding, is much lower in the close-up, than it is in the wide shot that follows and so forth. (01:08:40)
Continuity mistake: Cannon fire breaks a hole in the jail wall and inside the cell, the last pirate says, "You've no manner of luck at all," In the next shot from outside, escaping through the hole the pirate takes a huge leap forward and out to the right. After a close-up pan of Jack, in the next outside wide shot, that same pirate is still right beside the hole in the wall and is just starting to climb down the rocks below the hole. (00:35:40)
Continuity mistake: On Dauntless, when Elizabeth tells Gillete that the pirates can't die, she is wearing a loose braid in her hair. Later, when she is tying the cloth together in order to escape, she is wearing an almost perfect braid. And even later after leaving Dauntless, when rowing the boat towards the Black Pearl, her hair is messed up again. (01:43:35 - 01:50:35)
Answer: The curse needs the blood of everybody who took a coin from the chest. All the other pirates have already contributed so, as the movie opens, the only blood needed is Will's, substituting for his father. During the finale of the movie, Jack takes a coin from the chest, adding himself to the curse, so his blood is now required as well as Will's.
Tailkinker ★
But I didn't see any blood on the coins, and none of the pirates cut themselves, even before Will became part of the mix.
Yes, the other pirates did cut themselves before Will came into it, off-screen. The lack of blood on the coins can simply be explained as most of it dripping to the bottom of the chest, it being washed away by storms blown into the cave, or by the fact that they didn't drop that much blood on it in the first place.
When they had Elizabeth they believed she was Bill Turner's daughter, but they all thought the curse had failed, none of them had cut themselves so it makes zero sense.
They had been collecting back the coins for years. During that time they repaid their own blood. All they needed was the last coin and the blood of Bill Turner to break the spell.
lionhead